Argania spinosa (L.) Skeels is considered one of the most recalcitrant woody species in Morocco in terms of in vitro regeneration, mainly due to the high oxidative activity and limited embryogenic competence of this species.The current experiment investigated how different auxin/cytokinin combinations and light conditions affect callus induction and subsequent somatic embryogenic development using leaf and petiole explants harvested from plantlets subjected to extended in vitro culture.There was a significant difference in the rate of necrosis in leaf explants (55%) compared to petioles (33%), which suggests that the former is more sensitive to oxidative stress.However, the morphogenic potential of leaf material was higher, with a callus induction rate of 62% compared to petioles (37%), with low levels of contamination in all explant types.Callogenesis could not take place in complete darkness and was least responsive on a medium supplemented with 0.5 mg L -1 6-benzylaminopurine (BAP) and 2 mg L -1 2,4-dichlorophenoxyacetic acid (2,4-D).When 0.5 mg L -1 BAP was combined with 0.5 or 3 mg L -1 2,4-D, nodular callus appeared at high frequency (50% in leaf explants), with the highest callus frequency occurring under light (up to 92% with 0.5 mg L -1 BAP and 0.5 or 3 mg L -1 2,4-D).Histological analysis showed small, isodiametric, meristematic cell aggregates, early globular-like structures, and extensive deposition of callose.These results are consistent with embryogenic properties.However, embryogenesis remained arrested at the pre-globular stage, representing a major limitation for regeneration.
Toufik et al. (Mon,) studied this question.